This invention relates to novel liquid crystal compounds and liquid crystal compositions containing the same.
Display elements utilizing liquid crystals have been generally used for watches, electric calculators, etc. These liquid crystal display elements utilize the optical anisotropy and dielectric anisotropy of liquid crystal substances, and the liquid crystal phases include nematic liquid crystal phases, smectic liquid crystal phases and cholesteric liquid crystal phases. However, among these, display elements utilizing nematic liquid crystals have been most generally pratically used. Namely, correspondingly to the electro-optical effect which has been applied to liquid crystal display, display elements are classified into TN (twisted nematic) type, DS (dynamic scattering) type, guest-host type, DAP type, etc., and the various properties required for liquid crystal substances used for these respective display elements. As for such liquid crystal substances, those which exhibit liquid crystal phases within a temperature range as broad as possible in the natural world are preferable. However, it is the present situation is such that there is no substance which alone satisfies the above conditions, but several kinds of liquid crystal substances are mixed with one another or with non-liquid crystal substances, for practical use. The above substances are required to be stable to moisture, heat, air, etc. and it is further required that the threshold voltage and saturation voltage necessary for driving display elements are as low as possible.
Further, liquid crystal compositions having a large value of optical anisotropy (hereinafter abbreviated to .DELTA.n) can inhibit occurrence of color unevenness due to a partial non-uniformity of the distance between substrates of liquid crystal display elements, to thereby reduce the distance between the substrates, which results in an advantage that it is possible to increase the intensity of an electric field even under the same impressed voltage. Thus, compounds having a large .DELTA.n are required.
The object of the present invention is to provide novel liquid crystal compounds suitable for such use applications.